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Re: Block-level CRC checks

From: "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov>
To: "Paul Schlie" <schlie(at)comcast(dot)net>,"Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: "Brian Hurt" <bhurt(at)janestcapital(dot)com>,<pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Block-level CRC checks
Date: 2008-10-01 19:17:03
Message-ID: 48E3865E.EE98.0025.0@wicourts.gov (view raw or flat)
Thread:
Lists: pgsql-hackers
>>> Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote: 
> Paul Schlie <schlie(at)comcast(dot)net> writes:
>> - yes, if you're willing to compute true CRC's as opposed to
simpler
>> checksums, which may be worth the price if in fact many/most data
>> check failures are truly caused by single bit errors somewhere in
the
>> chain,
> 
> FWIW, not one of the corrupted-data problems I've investigated has
ever
> looked like a single-bit error.  So the theoretical basis for using
a
> CRC here seems pretty weak.  I doubt we'd even consider automatic
repair
> attempts anyway.
 
+1
 
The only single-bit errors I've seen have been the result of a buggy
driver for a particular model of network card.  The problem went away
with the next update of the driver.  I've never encountered a
single-bit error in a disk sector.
 
-Kevin

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